IGF-1 LR3
Potent, long-acting IGF-1 analogue. Real anabolic signalling, real risk profile.
What it is
A modified insulin-like growth factor 1 with reduced binding-protein affinity, extending its half-life considerably.
What it does
Activates IGF-1 receptor signalling, which drives cell growth and proliferation.
Does it work?
The mechanism is not in doubt — which is exactly why caution is warranted. Growth signalling acts on all proliferating cells, and long-term human safety data in healthy adults is absent. Prohibited in competitive sport.
Claims vs data
Each marketing claim, tagged by what the evidence actually supports.
| Increases muscle protein synthesis | partially true |
| Safe for long-term use | overreach |
Reference figures
Quoted from published reference material. These are not Peptuity recommendations.
The evidence, counted
Live counts from Europe PMC and ClinicalTrials.gov.
37 publications indexed, but only 1 randomised controlled trials and 0 registered interventional studies. Human evidence exists but is thin.
query: "IGF-1 LR3" · checked 2026-08-07
Most-cited literature
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Impaired actions of insulin-like growth factor 1 on protein Synthesis and degradation in skeletal muscle of rats with chronic renal failure. Evidence for a postreceptor d
Ding H, Gao XL, Hirschberg R, Vadgama JV, Kopple JD. · J Clin Invest 1996 · 99 citations
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Extracellular signal-regulated kinase and phosphoinositol-3 kinase mediate IGF-1 induced proliferation of fetal sheep cardiomyocytes
Sundgren NC, Giraud GD, Schultz JM, Lasarev MR, Stork PJ, Thornburg KL · Am J Physiol Regul Integr Comp Physiol 2003 · 97 citations
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Insulin-Like Growth Factor-1 (IGF-1) and Its Monitoring in Medical Diagnostic and in Sports
Bailes J, Soloviev M. · Biomolecules 2021 · 92 citations
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HER receptor signaling confers resistance to the insulin-like growth factor-I receptor inhibitor, BMS-536924
Haluska P, Carboni JM, TenEyck C, Attar RM, Hou X, Yu C, Sagar M, Wong · Mol Cancer Ther 2008 · 85 citations
Regulatory status
Formal, dated regulatory actions.
WADA — Prohibited List 2026
Prohibited in sport — WADA S2 (peptide hormones, growth factors and related substances)
Common questions
What does LR3 mean?
A modified IGF-1 with an arginine substitution and 13 extra residues, reducing binding-protein affinity and extending its half-life considerably.
Why the cancer caution?
IGF-1 signalling drives growth in all proliferating cells, not just muscle. Long-term human safety data in healthy adults simply does not exist.
Is it detectable in doping control?
It is prohibited and tested for. Detection methods exist and have been applied in sanctions.